Flash Flood Warning 1, NWS Spokane, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
430 AM PDT FRI SEP 14 2007

.SYNOPSIS...
A VERY DRY RIDGE OF HIGH PRESSURE WILL RESIDE OVER THE INLAND
NORTHWEST THROUGH THE WEEKEND. THIS RIDGE WILL BRING PLENTY OF
SUNSHINE DURING THE DAYTIME HOURS AND COOL OVERNIGHT TEMPERATURES.
BY SUNDAY NIGHT A TROUGH OF LOW PRESSURE WILL SLIDE OVER THE
REGION. THIS WILL BRING COOLER CONDITIONS THROUGH AT LEAST THE
MIDDLE OF NEXT WEEK.

&&

.DISCUSSION...
TODAY AND TONIGHT...SATELLITE INDICATES A BROAD REX BLOCK PATTERN
OVER WESTERN CONUS AND WESTERN CANADA...WITH THE ASSOCIATED CLOSED
LOW FEATURE VISIBLE ON SATELLITE AS AN AREA OF CIRCULATION OVER
OREGON. A DEFORMATION AXIS OF CONVECTIVE DEBRIS IS VISIBLE WELLING
UP FROM OREGON AND INTO SOUTHERN WASHINGTON THIS MORNING. LATEST
MODEL RUNS ARE REMARKABLY SIMILAR WITH THE OVERALL FIELD OF MOTION
AROUND THE REGION. SLIGHT UPPER LEVEL COOLING ASSOCIATED WITH THE
DEFORMATION AXIS WILL CROSS THE FORECAST AREA TODAY SLIGHTLY
DECREASING MID LEVEL STABILITY...BUT AIR MASS WILL REMAIN TOO DRY
FOR ANY STORMS OR EVEN SIGNIFICANT CLOUD DEVELOPMENT BEYOND
OCCASIONAL TRANSITING PATCHES OF CIRRUS AND HIGH AC TO FILTER THE
SUN OCCASIONALLY. AT THE SURFACE...A WEAK AND NEBULOUS THERMAL
TROUGH WILL SET UP OVER THE BASIN LEADING TO LIGHT WINDS AND HIGH
TEMPERATURES A DEGREE OR TWO HIGHER THAN YESTERDAY MAX TEMPS. THE
ONLY SIGNIFICANT WEATHER ISSUE TODAY WILL BE THE AREAL EXTENT AND
OPACITY OF SMOKE FROM THE MANILA CREEK FIRE NEAR KELLER. THIS SMOKE
FIELD WILL CHOKE MUCH OF THE DEEP/WESTERN COLUMBIA BASIN THROUGH
THIS MORNING BEFORE THE INVERSION MIX OUT ALLEVIATES THE SITUATION
SOMEWHAT. THIS SMOKE MAY EVEN BLOCK ENOUGH SUN TO IMPACT HIGH
TEMPERATURES IN THE DEEP BASIN AND RETARD THEM FROM REACHING
YESTERDAYS HIGHS DESPITE A GENERAL WEAK WARMING TREND ELSEWHERE.

TONIGHT LITTLE CHANGE IN THE OVERALL PATTERN...EXCEPT A WEAK
MARINE PUSH THROUGH THE CASCADES GAPS WILL BRING MORE WIND TO THE
WESTERN ZONES...AND PERHAPS SLOSH THE SMOKE OVER THE EASTERN
BASIN TONIGHT. /FUGAZZI

SATURDAY THROUGH SUNDAY NIGHT...ON SATURDAY MAIN EMPHASIS WILL
REMAIN WITH MOISTURE ROTATING NORTH AROUND A CUTOFF LOW OFF THE
NORTHERN CALIFORNIA COAST. MODELS PRETTY CONSISTENT WITH TAKING AN
AREA OF ELEVATED MOISTURE AND INSTABILITY NORTH TO NEAR OR JUST
SOUTH OF THE CAMAS PRAIRIE AND BLUE MTNS. GIVEN THAT THESE AREAS
ARE ON THE FRINGES OF THE MID LEVEL MOISTURE...AND ALSO DUE TO A
VERY DRY LOW LEVEL AIR MASS...FORECAST WAS KEPT DRY WITH 5-10
POPS. ON SATURDAY NIGHT INTO SUNDAY WHAT IS LEFT OF THE MID LEVEL
MOISTURE FROM THE CUTOFF LOW WILL GET PICKED UP BY THE UPPER LEVEL
FLOW IN ADVANCE OF AN APPROACHING COLD FRONT. THIS MOISTURE WILL
COMBINE WITH WEAK INSTABILITY FOR A SLIGHT CHANCE OF SHOWERS
OVER THE HIGHER TERRAIN OF SE WASHINGTON AND THE CENTRAL IDAHO
PANHANDLE. THE COLD FRONT ITSELF WILL BE NEAR THE CASCADES LATE
SUNDAY AFTERNOON...CROSSING THROUGH THE AREA SUNDAY NIGHT. GIVEN
THE INITIALLY DRY LOW LEVEL AIR MASS...DOWNSLOPE WEST-SOUTHWEST
FLOW OFF THE CASCADES ALONG AND AHEAD OF THE FRONT...AND THE FAST
MOVEMENT OF THE FRONT...PRECIPITATION CHANCES DO NOT LOOK GOOD
WITH ONLY 10-20 POPS. A TIGHTENING WEST-EAST PRESSURE GRADIENT
MAY LEAD TO LOCALLY BREEZY CONDITIONS IN THE WENATCHEE RIVER
VALLEY EAST INTO THE COLUMBIA BASIN AND EASTERN WASHINGTON. JW

MONDAY THROUGH THURSDAY...MODELS CONSISTENT WITH A LONG WAVE
TROUGH SETTLING IN OVER THE AREA. DETAILS STILL DIFFER THOUGH AS
BOTH GFS AND ECMWF HINT AT A CLOSED LOW DEVELOPING AS A SYSTEM DROPS
DOWN THE EAST SIDE OF THE OFFSHORE RIDGE. FOR THIS REASON KEPT
FORECAST CHANGES MINIMAL...WHICH CALLS FOR COOLER AND SLIGHTLY
GREATER CHANCES FOR PRECIPITATION MON THRU WED...FOLLOWED BY DRIER
CONDITIONS THURSDAY.  JW

&&

.AVIATION...
EARLY MORNING LLWS POSSIBLE AT KGEG AND KSFF TAF SITES UNTIL
INVERSION ERODES AROUND 16Z. LARGE AREA OF SMOKE WITH MVFR
VISIBILITIES AND LOCAL IFR VISIBILITIES WILL PERSIST OVER COLUMBIA
BASIN WEST OF KGEG UNTIL 18Z...WITH IMPROVEMENT TO LOCAL MVFR
VISIBILITIES AFTER 18Z. OTHERWISE VFR CONDITIONS EXPECTED THROUGH
12Z SAT.

&&

.PRELIMINARY POINT TEMPS/POPS...
SPOKANE        82  50  81  53  77  49 /   0   0   0   0   0  20
COEUR DALENE  83  45  82  49  76  48 /   0   0   0   0   0  20
PULLMAN        83  44  81  44  77  46 /  10   0   0   0  10  20
LEWISTON       88  55  86  54  80  56 /  10  10   0   0  10  10
COLVILLE       86  45  85  43  79  45 /   0   0   0   0   0  20
SANDPOINT      80  42  80  44  75  49 /   0   0   0   0   0  20
KELLOGG        81  48  79  51  75  45 /   0   0   0   0   0  20
MOSES LAKE     84  51  86  51  79  50 /  10  10   0   0   0  10
WENATCHEE      85  59  84  57  80  54 /  10  10   0   0  10  10
OMAK           88  52  87  50  81  49 /   0   0   0   0  10  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&